MYSTERY CLOUD LAID TO ERUPTION OF VOLCANO NOT YET LOCATED

By WALTER SULLIVAN

Published: March 6, 1982

The ''mystery'' cloud circling the earth is not really a mystery, according to a scientist at the National Aeronautics and Space Administration who has been collecting worldwide observations of the phenomenon.

It is a result, Dr. M. Patrick McCormick said yesterday, of a volcanic eruption that threw a quarter-million tons of material into the stratosphere. But the volcano that produced the eruption, he said, has yet to be identified.

The cloud, Dr. McCormick said, has the earmarks of widely monitored clouds produced by three recent volcanic eruptions. One was that of Mount St. Helens in Washington on May 18, 1980. The other eruptions were of Ulawan, the highest mountain on the island of New Britain in the southwest Pacific, on Oct. 7, 1980, and of Alaid, the highest volcano in the Kurile Islands north of Japan, on April 27, 1981.

Dr. McCormick, of NASA's Langley Research Center in Virginia, has been observing the cloud with ground-based and airborne laser radars, or ''lidars.'' He has also assembled data from lidars overseas, tracing the cloud's movement around the globe. Such clouds are not ordinarily seen by the unaided eye, but may contribute to red sunsets.

No eruption violent enough to throw up such a cloud has been identified, but in a telephone interview Dr. McCormick said one of two eruptions in January may have been responsible. One occurred in eastern Zaire. The other was of Langila, a volcano in New Britain that erupted explosively on Jan. 11.

In neither case was there a report of a plume rising to the stratosphere, but Dr. McCormick said information from such places was meager. It is also possible, he added, that the eruption was on an island so remote it has not been reported. Satellite images, he said, are being examined for evidence of an eruption.

The cloud was first recorded 10 miles overhead on Jan. 23 by the lidar of Kyushu University in Japan, where Motokazu Hirono found echoes typical of volcanic debris. At such high elevations the debris usually consists of coagulated sulfur compounds and water droplets.

Five days later the cloud was recorded as it drifted westward by a lidar at the observatory on Mauna Loa Volcano in Hawaii. NASA's lidar in Virginia picked it up on Feb. 10. A West German station at Garmisch-Partenkirchen began to do so on Feb. 2.

The airborne NASA lidar was flown from Virginia to Costa Rica and out over the Pacific Ocean, charting the structure of the cloud. NASA also planned to send a U-2 plane from Topeka, Kan., into the cloud today to collect samples for analysis.

While some particles thrown into the stratosphere by Mount St. Helens are presumably still there, they have been spread so uniformly and thinly that they are masked by material from more recent eruptions. Most researchers have concluded that the Mount St. Helens eruption did not have an observable effect on climate.